Process for the sensitization of photoconductors



United States Patent 3,287,119 PROCESS FOR THE SENSITIZATION 0FPHOTOCONDUCTORS Helmut Hoegl, Geneva, Switzerland, assignor, by mesneassignments, to Azoplate Corporation, Murray Hill NJ.

No Di'awing. Original application July 24, 1961, Ser. No. 125,984.Divided and this application Jan. 18, 1965, Ser. No. 426,358 Claimspriority, application Germany, May 29, 1959,

K 37,853; July 28, 1960, K 41,311 30 Claims. (Cl. 96-1.5)

This application is a division of copending application Serial No.125,984, filed July 24, 1961, now abandoned,

which, in turn, is a continuation-in-part of application Serial No.30,752, filed May 23, '1960, and also now abandoned.

Electrophotographic material normally consists of a support on whichthere is a photoconductive substance, this coating being provided in theabsence of light with an electrostatic charge. Then, the material isexposed to light behind a master, or an episcopic image is projectedthereon, so that an electrostatic image is formed which corresponds tothe master. This image is developed by being briefly contacted with aresin powder, whereupon a visible image is formed which is fixed byheating or by the action of solvents. In this way, an image of themaster which is resistant to abrasion is obtainedelectrophotographically.

In the electrophotographic process as described an increase in thesensitivity of the photoconductive coatings has already been attemptedby the addition of organic dyestuflfs, e.g. triphenylmethane, xanthene,phthalein, thiazine and acridine dyestufis, to the photoconductors.

The absorption maxima of the organic photoconductors are mostly in theultra-violet region of the spectrum. The-addition of these dyestuft'sensitizers achieves the result that the photoconductors becomesensitive to visible light. Generally, the dyestuflf sensitizers cause adisplacement of the available sensitivity from the ultraviolet region tothe visible region. With increased addition of dyestuif sensitizer, thesensitivity to visible light at first increases rapidly, but furtheradditions give an increase in sensitivity which is much less than wouldbe expected, and still further additions finally give no appreciableincrease in sensitivity. The dyestulf sensitizers have the disadvantagethat they color the coating considerably. In practice, the maximumachievable increase in sensitivity can seldom be utilized because thenthe photoconductor coatings have an intensity of color that isundesirable. Colorless or practically colorless photoconductor coatingsare desired, since colored material can be employed only in specialcases. If additions of dyestuff sensitizers are such as not to adverselyafiect the coloring of the coating for practical purposes, thesensitizing effect often does not meet the demands of general usage.Further, the dyestutf sensitizers have the disadvantage that they bleachout relatively quickly so that their sensitizing action tends to be lostduring the storage of the electrophotographic material.

A process for the sensitization of photoconductor coatings has now beenfound in which organic substances, containing polarizing residues andbeing capable of serving as electron-acceptors in a molecule complex,having low molecular weight, i.e. being non-resinous, being colorless orof pale color and having a melting point above room temperature, areadded to the photoconductor coatings.

Substances which are primarily of interest as photoconductor coatings inaccordance with the present process are those which can serve aselectron donors in molecule complexes of the donor/acceptor type (knownas Er-complex) and contain at least one aromatic or heterocyclic ring,which may be substituted. Such photoconductors include aromatichydrocarbons such as naphthalene, anthracene, benzanthrene, chrysene,p-diphenylbenzene, diphenyl anthracene, p-terphenyl, p-quaterphenyl,sexiphenyl; heterocycles such as N-alkyl carbazole, thiodiphenylamine,oxadiazoles, e.g., 2,5-bis-(p-amiuophenyl)-l,3,4-oxadiazole and itsN-alkyl and N-acyl derivatives; triazoles such as 2,5bis-(p-aminophenyl)- l,3 ,4-triazole and its N-alkyl and N-acylderivatives; imidazolones and imidazolthiones, e.g.,1,3,4,5-tetraphenyl-imidazolone-Z and1,3,4,5-tetraphenyl-imidazoltlnone-Z; N-aryl-pyrazolines, e.g.1,3,5-triphenyl-pyrazoline; hydrated imidazoles, e.g.,1,3-diphenyl-tetrahydroimidazole; oxazole derivates such as2,5-diphenyloxazole-2- p-dimethylamino-4,S-diphenyloxazole; thiazolederivatives such as 2-p-dia1kylaminophenyLmethyl-benzthiazole; as alsothefollowing:

Oxazoles and imidazoles described in German patent application K 35,586Iva/57b, filed Aug. 22, '1958. Acylhydrazones described in German patentapplication K 36,517 Iva/57b, filed Dec. 19, 1958. 2,2,4-triazinesdescribed in Germanpatent application K 36,651 Iva/57b, filed Ian. 7,1959.

Metal compounds of mercapto-benzthiazole, mercaptobenzoxazole andmercapto-benzimidazole described in German patent application K 37,508IVa/57b, filed Apr. 18, 1959.

Imidazoles described in German patent application K 37,435 Iva/57b,filed Apr. 9, 1959. Triphenylamines described in German patentapplication K 37,436 Iva/57b, filed Apr. 9, 1959.

Furans, thiophenes and pyrroles described in German patent application K37,423 IV a/ 57b, filed Apr. 8, 1959;

Amino compounds with multinuclear heterocyclic and multinuclear aromaticring system described in Ger- 111198511; patent application K 37,437IVa/57b, filed Apr. 9,

Azomethines described in German patent application K 29,270 IVa/57b,filed July 4, 1956.

Molecule complexes are defined in H. A. Staabs Einfuhrung in dietheoretische organische' Chemie (Introduction to Theoretical OrganicChemistry), Verlag Chemie, 1959, pp. 694-707, and by L. I. Andrews,Chemical Review, vol. 54, 1954, pp. 713-777. In particular, the donor/acceptor complex (r-complexes) and charge-transfer complexes which areformed from an electron-acceptor and an electron-donor are included. Inthe present case, the photoconductors are the electrondonors and thesubstances here called activatorsto dis tinguish them from the dyestutfsensitizers-are the electron-acceptors. The electron-donors have a lowionization energy and have a tendency to give up electrons. They arebases in the sense of the definition of acids and bases given by G. N.Lewis (H. A. Staab, as above, p. 600). The electron-donors primarilyconcerned in the present case are the photoconductors described above.These photoconductors consist of aromatic or heterocyclic systemscontaining a plurality of fused rings, or, alter natively, single ringshaving substituents which facilitate further electrophilic substitutionof the aromatic ring, socalled electron-repellent substituents, asdescribed by L. F. and M. F ieser, Lehrbuch der organischen Ohemie"(Textbook of Organic Chemist y) Verlag Chemie, 1954, p. 651, Table I.These are, in particular, saturated groups, e.g., alkyl groups such asmethyl, ethyl, and propyl; alkoxy groups such as methoxy, ethoxy andpropoxy; carbalkoxy groups such as carbmethoxy, carbethoxy andcarbpropoxy; hydroxyl groups, amino groups and dialkylamino groups suchas dimethylamino, diethylamino and dipropylamino.

The activators in accordance with the invention, which areelectron-acceptors, are compounds with a high electron-aflinity and havea tendency to take up electrons. They are acids in the sense of Lewisdefinition. Such properties are possessed by substances having stronglypolarizing residues or groupings such as cyano and nitro groups,halogens such as fluorine, chlorine, bromine and iodine; ketone groups,ester groups, acid anhydride groups, acid groups such as, carboxylgroups or the quinone grouping. Strongly polarizing electron-attractinggroups of this type are described by L. F. and M. Fieser in the Lehrbuchder organischen Chemie, Verlag Chemie, 1954, p, 651, Table I. .Of thesesubstances with amelting point above room temperature (25 C.) arepreferable, i.e. solid substances, because these impart a particularlylong shelf life to the photoconductive coatings as a result of their lowvapor pressure. Substances which are rather deeply colored such asquinones can be used, but those that are colorless or only weak in colorare preferable. Their absorption maximum should preferably be in theultra-violet region of the spectrum, i.e. below 4,500 A. Further, theactivator substances in accordance with the present process should be oflower molecular weight, i.e. between about 50 and 5000, preferablybetween about 100 and 1000, because with activators of lower molecularweight it is possible for reproducible results to be obtained insofar assensitivity is concerned. Also, the sensitivity remains constant overrather long periods, since substances of lower molecular weight, unlikethose of high molecular weight, undergo hardly any change duringstorage. The following are examples of such substances:

2-bromo-5-nitro-benzoic acid o-Chloronltrobenzene. 2-brom0benz0ic acidChloracetophenone. Z-chloro-toluene-t-sulphonic acid.-- 2-chlorocinnamicacid. Chloromaleic anhydride 9-chloroacridine 2-chloro-4-nitro-1-benzoicacid. B-chloroacridine 2-chloro-5-nitro-1-benzoic acid.6-c%0rt;gltrobenzene-5-sulpho- 3chloro-6-nitro-1-benzcic acid.

or e. 1 i-chloro-ii-nitro-l-benzoic acid-.-- Mucochloric acid.4-chloro-2-hydroxy-benzoic'aci Mucobromic acid.kchloro-l-phenol-Zt-sulphonic aci Styrenedibromide.2-chloro-3-nitro-1-t0luene-5-sul- Tetrabromo xylene.

phonic acid. 4-cizlorq3-niigo-benzene-phos- B-Trichlorolactic acidnitrile.

p omc ac Dibromosuccinic acids. Tripheuylchloromethane. 24-dichlorobenz0ic acid.-. Tetrachlorophthalic acid. Dibromomaleicanhydride Tetrabromophthalic acid. 9,10-dibromoanthraceneTetraiodophthalic acid. 1,5-dichloronaphthalene-.- Tetrachlorophthalicanhydride. 1,3-dichloronaphthalene Tetrabrornophthalic anhydride.2,4-dinitro-l-chloronaphthalene--- Tetraiodophthalic anhydride.3,4-dieh1oro-nitrobenzene Tetzl actilcrophthalic acid monoe y es er.2,4-dich1oro-benzisatin Tetrabromophthalic acid monoethylester.2,6-dichloro-benzaldehyde Tetraiodophthalic acid monoethyiester.Hexabromonaphthalle anhydride Iodoiorm. bz-l-cyano-benzanthrone Fumaricacid dinitrile. Cyan acetic acid Tetracyanethylene. acyanocinnamic acids-Tricyano-benzene. 1,5-dicyanonaphthalenc 3,5dinitrobcnzoic acid2,4-dinitro-l-chloronaphthalene. 3,5-dinitrosalicylic acid1,4-dinitro-naphthalcne. 2,4-dinitro-1-benzoic acid1,5-dinitro-naphthalcne. 2,4-dinitro-1-t01uene-6sulionic acid-1,8-dinitronaphthalcne. 2,6-rlia1itro-1-phenol-4-sulphonic2-nitrcbenzoic acid.

ac 1,3-dinitro-benzene 3-nitrobenzoic acid.

' 4-nitrobenzoic acid.

3-nitro-4-ethoxy-benzoic acid. 3-nitro-2-cresol-5-sulphonic acid.

6-nitro4-methy1-l-phenoi-2-su1- B-nitrobarbituric acid.

phonic acid. Z-nitrobenzenesul hinic acid 4-nitro-acenaphthene.3-nitro-2-hydroxy -1-benzoic acid 4-nitro-benzaldehyde.2-nitro-1-phen0l-4-sulphonic acid 4-nltro-phenol.a-nitro-N-butyl-carbazole Picryl chloride. 4-nitrobiphenyl2,4,7-trinitro-fluorenone. Tetranitrofluorenone s-Trinitro-benzene.2,4,6-trinitro-anisole- Anthraquinona; l-chloro-Z-methyl-anthraquinone.Anthraquinone-Zcarboxylic acid--- Duroquinone. Anthraquinone-2-a1dehyde2,6-dichloroquinone. antliiliiaiquinoneisulphonic acid1,5-diphenoxy-anthraquinone.

an e. Anthgaquinone-ZJ-disulphonic 2,7-dinltr0-anthraquinone.

Anthraquinone-2,7-disulphonic 1,5-dich1oro-anthraquinone.

acid bis-anilide. Anthraquinone-Z-sulphonic acid1,4-dimethyl-anthraquinone. i

dimethylamide. Acenaphthenequinone 2,5-dichloro-benzoquinonc.

Anthraquinone-2-sulphonic acid methylarnide.

Acenaphthenequinone dichloride- Benzoquinone-ll-methyli-chloro-anthraquinoue.

knitro-l-phenol-iasulphonic acid. Picric acid.

1,2-benzanthraquinone Z-methylanthraquinone.

Bromanil Naphthoquinone-LZ.

1-chloro-4-nitro-anthraquinone- Naphth0qu1none-1,4.

Chloranil Pentacenequmone.

l-chlor-anthraquinone Tetracene-7,12-qumone.

Chrysenequinone. 1,4-toluquinone.

Thymcquinone -2,5,7,IO-tetrachloropyrenequlnone.

2,3-dichloro-naphthoquinone-1,4.

1,5-dich1oro-anthraquinone.

The quantity of the solid, non-resinous, substantially colorlesselectron-acceptors (activators) which is; best incorporated in thephotoconductive coating to be sensitized is easily established by simpleexperiments. The

photoconductive coating containing at least one photoconductor and atleast one solid, non-resinous, substani tially colorless,electron-acceptor, should contain the photoconductor andelectron-acceptor in proportions ranging from substantially less than,equal amounts to a substantial excess of the photoconductor with respectto the: 1 electron-acceptor. The optimum of the proportions 1 variessomewhat according to the substance used. Generally, minor amounts areused, i.e. from about 0.1 to. about 300 moles, preferably from about 1to about150 conductor and at least one solid, non-resinous, substan-.

tially colorless electron-acceptor, it isalso very useful to. havepresent the photoconductor and the electron-ac-.

ceptor in proportions ranging from substantially less than equal amountsto a substantial excess of the electronacceptor with respect to thephotoconductor. Theseproportions in which minor amounts of thephotocon-v ductor are added to the activator vary according to thesubstance used; however, in general, amounts from about 0.1 to about 300moles, preferably from about 1 to about 50 moles photoconductor per 1000moles activator are used. In some cases, it is also possible to use more1 than 300 moles photoconductor or activator per .1000 moles activatoror photoconductor, respectively, butby exceeding the above range thedark decay of the mixture usually increases, and in such cases coatingsmade 1 therefrom are inferior.

tors such as naphthalene, whose initial sensitivity is very slight, tobe given adequate sensitivity for the production of satisfactory imagesby electrophotographic processes.

Furthermore, by addition of minor amounts of photoconductors toactivators, photoconductive mixtures are obtained which havephotoconductivity much higher, than could be expected from the amount ofthe photoconducfor added to the activator. photoconductivity may beobtained by the addition of dyestuff sensitizers in the same amounts asin the photoconductor-activator mixtures in which the photoconductor, ispresent in a major amount.

moles of electron-acceptor per- 1000 moles of photoconi ductor.Alternatively, it has also been found that in the photoconductivecoatings containing at least one photo- Mixtures of severalphotoconductors and activator sub 1 stances may also be used. Moreover,in addition to these sensitivity, particularly in the ultra-violetregion, and,

to visible light by a very small addition of dyestufi,

A further increase in the The coatings are treated in other respects inaccordance with the known processes of electrophotography, i.e. thephotoconductor substances are used in the form of thin, coherenthomogeneous coatings on a supporting material. The materials used assupports are primarily metals, such as aluminum, zinc, and copper;cellulose products, such as paper and cellulose hydrate; plastics, suchas polyvinyl alcohol, polyamides, and polyurethanes. Other plastics,such as cellulose acetate and cellulose butyrate, especially in apartially saponified form, polyesters, polycarbonates, and polyolefins,if they are covered with an electroconductive layer or if they areconverted into materials which have the above-mentioned specificconductivity, e. g. by chemical treatment or by introduction ofmaterials which render them electrically conductive, can also be used,as well as glass plates. In general, materials are suitable the specificresistance of which is less than ohm-cm, preferably less than 10 ohm-cm.

If paper is used as the supporting material, it is preferably pretreatedagainst the penetration of coating solutions, e.g., it can be treatedwith a solution of methyl cellulose or polyvinyl alcohol in water orwith a solution of an interpolymer of acrylic acid methyl ester andacrylonitrile in a mixture of acetone and methylethyl ketone, or withsolutions of polyamides in aqueous alcohols or with dispersions of suchsubstances.

For the preparation of the electrophotographic material, thephotoconductive compounds are preferably dissolved in organic solventssuch as benzene, acetone, methylene chloride or ethyleneglycolmonomethylether or other organic solvents or in mixtures of suchsolvents, and resins and the activators-and possibly also the dyestufisensitizers-are advantageously added thereto. These solutions are coatedupon the supporting material in the normal manner, e.g., by immersionprocesses, painting or roller application or by spraying. The materialis then heated so that the solvent will be removed.

A number of the compounds in question can be applied together to thesupporting material or the compounds can be applied in association withother photoconductive sub stances.

Further, it is often advantageous for the photoconductor substances tobe applied to the supporting material in association with one or morebinders, e.g., resins. Resins primarily of interest as additions to thephotoconductor coatings include natural resins such as balsam resins,colophony and shellac, synthetic resins such as coumarone resins andindene resins, processed natural substances such as cellulose ethers;polymers such as vinyl polymers, e.g. polyvinyl chloride, polyvinylidenechloride, polyvinyl acetate, polyvinyl acetals, polyvinyl alcohol,polyvinyl ethers, polyacrylic and polymethacrylic acid esters,isobutylene and chlorinated rubber.

If the photoconductive compounds in accordance with the invention areused in association with the resins described above, the proportion ofresin to photoconductor substance can vary very greatly. Mixtures offrom two parts of resin and one part of photoconductor substance to twoparts of photoconductor substance and one part of resin are .to bepreferred. Mixtures of the two substances in equal parts by weight areparticularly favorable.

For the displacement of sensitivity from the ultra-violet to the visiblerange of the spectrum, dyestufi sensitizers can be used in addition tothe activators. Even very small additions of sensitizer, e.g., less than0.01 percent, give good results. In general, however, 0.01 to 5 percent,and preferably 0.1 to 3 percent of dyestufi sensitizer is added to thephotoconductor coatings. The addition of larger quantities is possiblebut in general is not accompanied by any considerable increase insensitivity.

Some examples are given below of dyestufi sensitizers which may be usedwith good results, and some with very good results. They are taken fromSchultz Farbstofitabellen (7th edition, 1931, 1st vol.):

Triarylmet-hane dyestuffs such as Brilliant Green (No. 760, p. 314),Victoria Blue B (No. 822, p. 347 Methyl Violet (No. 783, p. 327),Crystal Violet (No. 785, p. 329), Acid Violet 6B (No. 831, p. 351);xanthcne dyestufis, namely rhodamines, such as Rhod-amine B (No. 864, p.365), Rhodamine 66 (No. 866, p. 366),Rhodamine G Extra (No. 865, p.366), Sulphorhodamine B (No. 863, p. 364) and Fast Acid Eosin G (No.870, p. 368), as also phthaleins such as Eosin S (No. 883, p. 375),Eosin A (No. 881, p. 374), Erythrosin (No. 886, p. 376), Phloxin (No.890, p. 378), Bengal Rose (No. 889, p.. 378), and Fluorescein (No. 880,p. 373); thiazine dyestufis such as Methylene Blue (No. 1038, p. 449);acridine dyestuffs such as Acridine Yellow (No. 901, p. 383), AcridineOrange (No. 908, p. 387) and Trypaflavine (No. 906, -p. 386); quinolinedyestuffs such as Pinacyanol (No. 924, p. 396) and Cryptocyanine '(No.927,. p; 397 cyanine dyestuffs, e.g., Cyanine (No. 921, p. 394) andchlorophyll.

For the production of copies with the electrocopying material, thephotoconductive coating is charged by means of, for example, a coronadischarge with a charging apparatus maintained at 6000-7000 volts- Theelectro-copying material is then exposed to light in contact with amaster. Alternatively, an episcopic or diascopic image is projectedthereon. An electrostatic image correspending to the master is thusproduced on thematerial. This invisible image is developed by contactwith adeveloper consisting of carrier and toner. The carriers used maybe, for example, tiny glass balls, iron powder or tiny plastic balls.The toner consists of a resin-carbon black mixture or a pigmented resin.The toner is used in a grain size of 1 to The developer may also consistof a resin or pigment suspended in a non-conductive liquid in whichresins may be dissolved. The image that is made visible by developmentis then fixed, e.g., by heating with an infra-red radiator to 100-1700., preferably -150 C. or by treatment with solvents such astrichloroethylene, carbon tetrachloride or ethyl alcohol, or steam.Images corresponding to the master characterized by good contrast effectare obtained.

If transparent supporting material is used, the electrophotographicimages can also be used as masters for the plrl'oduction of furthercopies on any type of light-sensitive s eets.

If translucent supports are used for photoconductive layers such as areprovided by the invention, reflex images can be produced also.

The application of the activators in accordance with the present processis not restricted to electrophotographic coatings, but can extend toother devices containing photoconductors, e.g., photoelectric cells,photoresistances, sensing heads or camera tubes and electroluminescentapparatus.

The invention will be further illustrated by reference to the followingspecific examples:

EXAMPLE 1 A solution containing 26 parts by weight of polyvinyl acetate(e.g., Mowilith 50), 25.6 parts by weight of naphthalene, 0.0415 part byweight of 2,3,7-trinitrofluorenone and 800 parts by volume of toluene isapnliedby means of a coating device to an aluminum foil. After thecoating has dried, direct images are produced thereon by theelectrophotographic process in the following manner: the coated foil isgiven a negative electric charge by corona discharge, exposed behind amaster to the light of a high-pressure mercury vapor lamp watts, at adistance of 30 cm.) for about 10 seconds and then dusted over with adeveloper.

The developer consists of tiny glass balls and a mixture of resin andcarbon black which has been melted together.

and then finely divided. A developer of this sort consists of, e.g., 100parts by weight of tiny glass balls (grain size: 100-400,11. approx.)and a toner (grain size: 20-50 approx.). The toner is prepared bymelting together'30 parts by weight of Polystyrol LG, 30 parts by weightof modified maleic acid resin (Beckacite K 105) and 3 parts by weight ofPeerless Black Russ 552. The melt 8 7 EXAMPLE 5 A solution of 26 partsby weight of polyvinyl acetate,:

21.6 parts by weight of1,5-diethoxynaphthalene and 0.258 part by weightof 1,2-benzanthraquinone in 800 Without the hexabromonaphthalicanhydride addition, an exposure of as much as 30 seconds gives an imagewhich contains background.

EXAMPLE 4 A solution'containing 18 parts by weight of polyvinyl acetate,18.2 parts by weight of 2,4-bis-(4'-diethylamino phenyl)-1,3,4-triazoleand 0.130 part by weight of tetrachlorophthalic anhydride to 500 partsby volume of toluene is applied to an aluminum foil and furtherprocedure is as described in Example 1. The exposure time with a l-wattincandescent lamp is 2 seconds.

Without the tetrachlorophthalic anhydride addition, the image obtainedafter an exposure of 1 minute is not free of background.

Explanations on Table A is then ground and screened. The finely dividedresin adparts by volume of toluene is applied to paperand the hares t0the Pa of f t not struck by during material is further processed asdescribed in Example 1. i exposur? i a Posmve Lmage of the master ecomesThe exposure time (125-watt high-pressure mercury vapor visible. It isshghtly heated and thereby fixed. lamp) is 20 seconds If. not to h g iWithout the 1,2-benzanthraqninone addition, the copy descl'lbed above,even an f": 0 two es W1 still has considerable background after anexposure of 80 not produce an electrophotographic image. Seconds EXAMPLE2 EXAMPLE 6 p 26 parts by weight of polyvinyl acetate 166 parts by 26parts by weight of polyvinyl acetate, 17.0 parts weight of fluorene and0.3602 part by weight of tetranitroby welaht 0f Pllfillanthmne d 9- P yWelght 0f fluorenone are dissolved in 800 parts byvolume oftoluchlofaflll are (1185011160 g t er 1n 300 parts -by volume ene. Thissolution is applied to an aluminum foil and of toluene- 5011111011 18 PPt0 P Y further procedure is as described in Example Exporoughenedaluminum foil and then the material ls fursum time if a 125 watthigbpressure mercury Vapor lamp ther processed as described InExample 1. If the mate-- is used, is 10 sticonds. t rial is exposed to a125-watt high-pressure mercury vapor Without the'tetranitrofiuorenoneaddition, the images lamp, an exposureffi 9 seconds Elves an Image freeof obtained even after an exposure of two minutes are not backgrqund e fWhereas wlthout the free of bakgmund, Le the expose-d parts are not f llchloraml addition there is heavy background even after dischargedand'therefore retain a certain amount of dean exposure of one mmute-tveloper. EXAMPLE 7 EXAMPLE 3 A solution containing 26 parts by weight ofpolyvinyl A solution of 26 parts by weight of polyvinyl acetate,acetate, 24.4 parts by weight of o-dianisidine and 0.0256 17.8 parts byweight of anthracene and 0.3357 part by part by weight ofdibromomaleicanhydride in 800 parts weight of hexabromonaphthalicanhydride in 800 parts by volume of toluene is applied to an aluminumfoil and by volume of toluene is applied to aluminum and further thematerial is further processed as described in Examprocedure is, asdescribed in Example 1. With a 125-watt ple 1. The exposure time(125-watt high-pressure merhigh-pressure mercury vapor lamp, theexposure time is cury vapor lamp) is 2 seconds. Without the dibromo- 4seconds. maleic anhydride addition, it is 10 seconds.

TABLE A No. A B C D E 1 P1ln1 tt,10 t(1 8 12 2 "if; y ace 8 par 5 8Anthraqulnone, 0.08 30 52:? (ca) 3 8 Anthraqulnone, 0.17 20 see. (b). 48 Anthmquinone, 0 25 20 see. (b). 8 0.001 sec. (b). s 0. 005 60sec. (b).7 8 0.010 60sec. (b). 8 8 0.030 90sec. (b). 8 0.050 90 see. (b). 8Anthraquinone, 0.17 0. 001 20 see. (b). n g dn 0.010 20sec. (b). g dn0.50 20sec. (b). 13--- 8 240 sec. (8). 14 8 Anthraqulnone, 0.25 180 sec.(3). Cyclized rubber, 10 parts (2). 8 240 see. (a). (ln 8 Anthraquinone,0.25 30 see. (a). Alter-chlorinated polyvinylchloride, 7parts (3)- 8 10see. (a). Polyvinylchloride, alterchlorinated, 7parts (3). 8Anthraquinone, 0.25 part 3 see. Maleic acid resin, 10 parts (4) 8 240sec. (a). do 8 Anthraquinone, 0.25 part 60 see. (a) Chlorinated rubber,10 parts (5) 8 20 see. (a). d 8 Anthraquinone, 0.25 part 10 see. (a).Chlorinated rubber, 10 parts (6) 8 20 see. (a). dn 8 Anthraquinone, 0.2510sec. (9,), dn 8 Libenzanthraquinone, 0.31 part 1-1.5 see. (3). (ln 8Hexabromouaphthahc anhydride, 0.80 part- 11.5 see. (a). dn 8 2,t,5,7-tetramtrofiuorenone, 0.43 part 1.5 see. (a). 8 Dlbromomalelcanhydride, 0.30 part; 4-6 see. (a). rln 8 Nitrogterephthalicacid-dimcthylester, 0.28 6-8 see. (a).

par 3() rln 8 Tetracyano ethylene, 0.15 part 4-6 see. (a). 31 dn 81,3,5-trlnltrobenzene, 0.25 part 1.5-2 see. (a).

Column A: Quantity and kind of binder used. In all cases, the quantitiesstated were dissolved in 200 parts by volume of toluene.

Column B: Quantity of the photoconductor.

damine B extra).

Column E: Time of exposure, using:

(a) a 250 watt photographic lamp (Philips Photocrescenta Column D:Quantity of dyestufi sensitizer used (Rho- (b) a customary wattincandescent lamp.

In all The tests were carried through under the same experimentalconditions, with the exception of the variations stated in the table.

(1) The polyvinyl acetate used was the product commercially availableunder the registered trademark Mowilith C.

(2) The cyclized rubber usedwas the product commercially available underthe registered trademark "Pliolite S-SD.

(3) The afterchlorinated polyvinylchloride used was the productcommercially available under the registered trademark Rhenofiex.

(4) The maleic acid resin used was the product commercially availableunder the designation Alrosat.

(5) The chlorinated rubber used in Table A, col. A, under N0. 21 (5 wasthe product commercially available under the registered trademark ParlonS-5 cps.

(6) The chlorinated rubber used in Table A, col. A, under N0. 23 (6) wasa product commercially available under the registered trademark Pergut8-40.

The following Table B shows further examples of various photoconductorswhich were activated,.and the reduction in exposure time caused by theactivators:

TABLE B A B C 26 Chloranil Hexabromonaphthalie anhydride 2,4,5,7-tetranitr0fiuorenone Hediagromonaphthalic anhy- 1 e.2,4,5,7-tetrauitrofluorenone 1,5-dinitr0naphthalene l,4-benzoquinoueOhloraml 3,5-dinitrosalicylic 301d--. Dibromomaleic anhydrideTetrachlorophthalic anhydride Hexabromonaphthalic anhydride-Picrylehloride 2,4.5,7-tetranitrofluorenone- Chloranil 13.6hydroquinonedimethylether.

m: PST;

25.6 naphthalene- 26 21.6 1,5-diethoxynaphthalene.

15.4 acenaphthene Dibromomaleic auhydride Hexabromonaphthalic an.hydridePicrylchloride 15.2 acenaphthylene- Hexabrornonaphthalrc anhydride.2,4,5,7-tetranitrofluorenone Chloranil 1,2-benzanthraquinone-Tetrachlorophthalic anh Picrylchloride 15.4 dlphenyl Chloranll 1,2-benzanthraquino Tetrachlorophthalic anh Hexabromonaphthalic anhydridPicrylchloride Chloranil 24.4 o-dianisidiue 16.6 finorene1,2-benzanthraquinone Hexabrornonaphthalie anhydride- Plcrylchlon'de3,5dinitrosalicylic aeid 1,2-benzanthraquin0ne Dibromorualeic anhydrideTetrachlorophthalic auhydride 2,4,5,7-tetranitrofluorenoue Benzoquinone17.8 anthracene 22.8 chrysene 52 Tetrachlorophthalic anhydrideHexabromonaphthalic auhydride Picrylchloride2,4,5,7-tetrar1itrofluorenone Benzoqntuone- Chloranil2,4,5,7-tetranitrofluorenone lA-benzoquinoue Chloranil3,5-dinitrosalicylie aeid 1.2-benzanthraquinone Dibromornaleie acidanhydri Tetraehlorophthalic anhydride-- Hexabromonaphthalic anhydridePicrylchloride 2,4,5,7-tetranitrofiuorenone 1,2-benzanthraquinoneDibrornomaleic anhydride. 'Ietrachlorophthalic anhydrideHexabromouaphthalic anhydride Picrylchloride 2,4,5,7-tetranltrofiuoreno16.9 diphenylamlne 26.9 2,2 -dinaphthylamine.

17.8 phenanthrene TABLE B-C0ntinued 19.3 Z-phenyl-indole 26 16.7carbazole 19.9 thiodiphenylamine--- 25.482,4-bis-(4-diethylaminophenyl)-1,3,4- oxadiazole.

18.2 2,4-bis-(4'-diethylaminophenyl)-l,3,+ triazole.

Explanations on Table B The table describes a series of experimentscarried through for improving the photoconductivity of organicsubstances by adding activators.

In Column A the quantity and nature of the substance used is stated. Thesubstances marked with a yielded no electrophotographic images evenafter an exposure time of several minutes. 7

In Column B the quantity of the binder used is stated. In all of thecases, polyvinyl acetate having a K-value of 50 was used. Binder,photoconductive substance, and activator were dissolved in toluene,coated onto an aluminum foil, and dried.

In Column C the substance used as activator is stated. In all of thecases 1 mol of the activator stated under C was used per moles of thesubstance stated under A.

In Column D the reduced time of exposure is stated which is required toproduce images equal in quality to those produced without the additionof an activator. In those cases where a prolonged exposure of thephotoconductor yielded not even a weak image (marked with a thecalculation of the reduced time of exposure was based on the longestexposure used for the unactivated photoconductor substance.

- Alternatively, the increase in sensibility obtained by the addition ofactivating substances may be taken from. a comparison of the degrees ofblackening obtained with the activated photoconductive layer and withthe unactivated photoconductive layer, under the same customary stepwedge (e.g. Kodak No. 2 density strip with color patches).

EXAMPLE 8 A solution containing 20 parts by weight ofafterchlorinated'polyvinyl chloride with a content of chlorine from 61.7to 62.3 percent and K-value from 59 to 62, 18.01 parts by weight of2,4,5,7-tetranitrofluorenone and 0.216 part by weight of1,5-diethoxynaphthalene dissolved in a mixture of 450 parts by volumetoluene and parts by volume butanone is applied to an aluminum foil. Thesubsequent procedure is that described in Example 1. The exposure time,with a 100 watt incandescent lamp at a distance of 30 centimeters is 2seconds.

Without the addition of 1,5-diethoxynaphthalene the exposure time isabout 40 seconds.

1 1 In the following table, the exposure times are given, which wereobtained when using other hotoconductors instead of the1,5-diethoxynaphthalene. I Exposure time;

EXAMPLE 9 A solution of 12 parts by Weight of chlorinated rubber (Pergut8-40), 5.04 parts by weight of 1,3-dinitrobenzone and 0.106 part byweight of anthracene in 150 parts by volume of toluene is applied to apaper foil and the material is further processed as described inExample 1. The exposure time (125 watt high pressure mercury vapor lamp)is 20 seconds. Without the anthracene addition, even after an exposuretime of 80 seconds, only traces of animage were obtained. This meansthat the exposed parts of the coating were not discharged and thereforestill attracted developer.

In the following table the exposure times are given, which wereobtained, when using other photoconductors instead of the1,3-dinitrobenzene.

Exposure time (seconds) Photoconductors (parts by weight):

2,2'-dinaphthylamine (0.180)

2,2'-dinaphthylamine, the exposure time is about 10 sec-.

onds.

EXAMPLE 12 To a solution containing 28.6 parts by weight of tetralchlorophthalic acid anhydride and 20 parts by weight of afterchlorinatedpolyvinyl chloride in a mixture of 150 parts by volume of butanone and450 parts by volume 1 of toluene, X parts by weight of photoconductorand Y parts by weight of dyestuft sensitizer are added. In the followingtable, the amounts; of, the hotoconductor and sensitizer are giventogether with the corresponding exposure times. It is advantageous todissolve the dyestuff sensitizer in a .small amount of ethyleneglycolmonomethyl ether before adding it to the solution. The latter is appliedto a paper base material and further processed as described inExample 1. The light source used throughout was a 125-watt high pressuremercury vapor lamp and the distance between this lamp and the mate-.

rial exposed was about 30 centimeters.

Photoconductor X parts Dyestufi sensitizer Y Exposure by weight Parts byweight ime (Seconds) None None ca. 200 0.39 N-ethylcarbazo1e -do 9 Do0.30 Rhodamine B extra 2-3 0.54 2,2-dinaphthylamine None 4-5 Do 0.30Rhodamine B extra 2 0.73 2,5-bis-(4'-diethylamino- None -1 4phenyl)-1,3,4-oxdiazole.

Do 0.30 Rhodamine B extra..-" 1-2 0.025 Basischreinblau 3 G 2 0.015Brillantgreen extra 3 0.015 Kristallviolet 2 0.015 Methylenb1ue 0. 5 yvinylcarbazole 0.30 Rhodamine B extr 9 Do None 20 EXAMPLE 10 A solutioncontaining 20 parts by weight of the afterchlorinated polyvinyl chloridementioned in Example 8, 21.02 parts by weight of benzile and 0370 partby weight of benzidine in a mixture of 450 parts by volume of tolueneand 150 parts by volume of butanone is applied to an aluminum foil andthe material is further processed as described in Example 1. Theexposure time (125 watt high pressure mercury vapor lamp at a distanceof 30 centimeters) is 10 seconds. Without the addition of the benzidineactivator, even after an exposure time of 4 minutes, noelectrophotographic image could be obtained.

In the following table, the exposure times are given which were obtainedwhen using hotoconductors other than benzidine.

Exposure time Photoconductors (parts by weight): (seconds)2,2'-dinaphthylamine (0.540) 20 2,5-bis-(4'-diethylamino-phenyl) 1,3,4oxdiazole (0.730) 5 Poly-N-vinylcarbazole (0.390) 30 EXAMPLE 11 Asolution containing 6.2 parts by weight of afterchlorinated polyvinylchloride, 3.94 parts by weight of 1,5-dichloronaphthalene and 0.145 partby weight of 2,5-bis- (4'-diethylaminophenyl)-1,3,4-oxdiazole in amixture of 135 parts by volume of toluene and 45 parts by volume ofbutanone is applied to a paper base and is further processed asdescribed in Example 1. The exposure time (125 watt high pressuremercury vapor lamp at a distance of 30 centimeters) is 10 seconds.Without the addition of the oxdiazole compound, even after an exposuretime of 40 seconds, no image could be obtained. When the oxdiazolecompound is replaced by 0.120 part by weight of EXAMPLE 13 A solution isprepared, containing 57.2 parts by weight:

of tetrachlorophthalic acid anhydride and 65 parts by weight ofafterchlorinated polyvinyl chloride in 700 parts by volume toluene andsufficient butanone is added to make up 1000 parts by volume. To 50parts by volume of the resulting stock solution, one of thephotoconductors listed below is added, and the solution isapplied to analuminum foil and further processed as describedin.

Example 1. In the following table, the added photoconductors areindicated, and the corresponding exposure- As the light source, a -watthigh times are given. pressure mercury vapor lamp in a distance of about30 centimeters from the exposed material was used in all instances.

Exposure time 1 Image with heavy background,

13 Photoconductor (parts by Weight) Exposure time Continued (seconds)Phenanthrene (0.089) 60 Phenoxathin (0.100) 10 Stilbene (0.090) 302,3,5-triphenylpyrrole (0.153) 10 1,1'-dinaphthylamine (0.134) 301,2'-dinaphthylamine (0.134) 30 4'-tolyl-1-naphthylamine (0.116) 60Z-phenylindole (0.096) 60 Acenaphthene (0.077) 60 Diphenyl (0.077) 120N-methyldiphenylarnine (0.091) 30 4-hydroxy-diphenylamine (0.092) 30Phlorglucinediethyl ether (0.091) 120 EXAMPLE 14 57.2 parts by weight oftetrachlorophthalic acid anhydride and 65 parts by weight of polyvinylacetate are dissolved in sufiicient toluene to make up 1000 parts byvolume. To 50 parts by volume of this stock solution, one of thephotoconductors listed below is added and the coating solution isapplied to an aluminum foil and further processed as described inExample 1. The light source and the distance of the light source fromthe exposed material were the same as in the foregoing example.

Exposure time (seconds) EXAMPLE 15 29.62 parts by weight of phthalicacid anhydride and 33 parts by weight of afterchlorinated polyvinylchloride are dissolved in 670 parts by volume of toluene and 330 partsby volume of butanone. To 50 parts by volume of the resulting stocksolution, one of the photoconductors listed in the following table isadded; these coating solutions are applied to an aluminum foil, andfurther processed as described in Example 1. The light source and thedistance of the light source were the same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 1 60N-ethylcarbazole (0.10) 5 Anthracene (0.09) Chrysene (0.114) Pyrene(0.10) 10 2,2'-dinaphthylamine (0.134) 10 2,3,5-triphenylpyr1'ole(0.153) 10 N0 image obtained.

EXAMPLE 16 p 49.2 parts by weight of chloranil and 56 parts by weight ofafterchlorinated polyvinyl chloride are dissolved in a mixture of 1170parts by volume of toluene and parts by volume of butanone. Theresulting solution is filled up to 2000 parts by volume withchlorobenzene. To 100 parts by volume of this stock solution, one of thephotoconductors listed in the following table is added; the coatingsolution is applied to an aluminum foil and further processed asdescribed in Example 1. The light source and the distance of the lightsource were the same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 180Naphthalene (0.064) ca. 20 Hydroquinonedimethyl ether (0.070) 30N-ethylcarbazole (0.097) 10 Anthracene (0.090) 5 Chrysene (0.114) 15Pyrene (0.10) -1 10 o-Dianisidine (0.122) 5 2,6-dimethyl-naphthalene(0.078) 0 Hexamethylbenzene (0.081) 2,2'-dinaphthylamine (0.134) 1-22,5-bis-(4'-diethylaminophenyl)-1,3,4-oxdiazole (0.182) 12,3,5-triphenylpyrrole (0.153) 4 EXAMPLE 17 10.6 parts by weight of2-acetyl fluorene and 12 parts by weight of afterchlorinated polyvinylchloride are dissolved in parts of toluene and sufficient butanol tomake up 250 parts by volume of solution. To 50 parts by volume of thisstock solution, one of the photoconductors of the following table isadded. The solution is applied to an aluminum foil and further processedas described in Example 1. The light source and the distance of thelight source were the same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 1 180o-Dianisidine (0.120) 30 2,5-bis-(4' diethylaminophenyl)-1,3,4-oxdiazole 1 No image obtained,

EXAMPLE 18 44 parts by weight of 9 acetyl-anthracene and 48 parts byweight of afterchlorinatcd polyvinyl chloride are dissolved in 700 partsby volume of solution. To 50 parts by volume of the resulting stocksolution, one of the photoconductors of the following table is added.This solu-. tion is applied to an aluminum foil and further proc essedas described in Example 1. The light source and the distance thereof wasthe same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 1 180Hydroquinonedimethyl ether (0.069) 30 N-ethyl carbazole (0.097) 60Anthracene (0.089) 60 Hexamethylbenzene (0.081) 30 1 Image with heavybackground.

EXAMPLE 19 46.2 parts by weight of pyrene-3-aldehyde and 50 parts byweight of afterchlorinated polyvinyl chloride are dissolved in 670 partsby volume of toluene and sufficient butanol to make up 1000 parts byvolume of solution. To 50 parts by volume of the resulting stocksolution one of the photoconductors of the following table is added. Thesolution is applied to an aluminum foil and further processed asdescribed in Example 1. The light source 15 and the distance of thelight source were the same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 30Naphthalene (0.064) 20 Hydroquinonedimethyl ether (0.070) 20.N-ethylcarbazole (0.10) 10 Anthracene (0.090) 2O Chrysene (0.114) 20Pyrene (0.10) 20 Hexamethylbenzene (0.080) 20 2,2'-dinaphthylamine(0.135) 15 2,5-bis-(4'-diethylaminophenyl)-l,3,4-oxdiazole2,3,5-triphenylpyrrole (0.150) 20 EXAMPLE 20 13.1 parts by weight of1,4,5-trinitronaphthalene and 15 parts by weight of afterehlorinatedpolyvinyl chloride were dissolved in 180 parts by volume of toluene andsufiicient butanone to make up 250 parts by volume. To 50 parts of theresulting stock solution, one of the photoconductors of the followingtable is added in the amount indicated. This solution is applied to analuminum foil and further processed as described in Example 1. The lightsource and the distance thereof were the same as in Example 13.

Exposure time Photoconductor (parts by weight): (seconds) None 1 180N-ethylcarbazole (0.10) 30 Anthracene (0.09) 30 o-Dianisidine (0.12)2,5-bis-(4-diethylaminophenyl)-1,3,4-oxdiazole 1 Image with heavybackground.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:

1. A sensitized photoconductive layer comprising at least one solid,non-resinous, substantially colorless electron-acceptor, and a compoundhaving the formula in which R and R are fused ring ortho-arylene groups,at least one of the rings having a primary amine group attached thereto,and R is selected from the group consisting of hydrogen and lower alkyl;the layer contain-ing the photoconductor and the electron-acceptor inproportions ranging from substantially less than equal amounts to asubstantial excess of the photoconductor with respect to theelectron-acceptor and from substantially less than equal amounts to asubstantial excess of the electron-acceptor with respect to thephotoconductor,

16* =3. A sensitized photoconductive layer comprising at least onesolid, non-resinous, substantially colorless electron-acceptor, and acompound having the formula I in which R and R are fused ringortho-arylene groups,

at least one of the rings having a primary amine group attached thereto,and R is selected from the group consisting of hydrogen and lower alkyl;in proportions ranging from a'bout 0.1 to about 300 moles of theelectron-acceptor per 1000 moles of photoconductor.

4. A sensitized photoconductive layer comprising, at

least one solid, non-resinous, substantially colorlesselectron-acceptor, and a compound having the formula in which R and Rare fused ring ortho-arylene groups, at least one of the rings having aprimary amine group attached thereto, and R is selected from the groupconsisting of hydrogen and lower alkyl; in proportions ranging fromabout 0.1 to about 300 moles of the photoconductor per 1000 moles of theelectron-acceptor.

5. A sensitized photoconductive layer comprising at least one solid,non-resinous, substantially colorless electron-acceptor, and a compoundhaving the formula in which R and R are fused ring ortho-arylene groups,

at least one of the rings having a primary amine group attached thereto,and R is selected from the group consisting of hydrogen and lower alkyl;in proportions ranging from about 1 to about 50 moles of theelectronacceptor per 1000 moles of the photoconductor.

6. A sensitized photoconductive layer comprising at least one solid,non-resinous, substantially colorless electron-acceptor, and a compoundhaving the formula in which R and R are fused ring ortho-arylene groups,

at least one of the rings having 'a primary amine group attachedthereto, and R is selected from the group consisting of hydrogen andlower alkyl; in proportions ranging from about 1 to about 50 moles ofthe photo-.

conductor per 1000 moles of the electron-acceptor.

7. A layer according to claim 1 in which the electronacceptor is2,4,7-trinitrofluorenone.

8. A layer according to claim 1 in which the elcctronacceptor istetranitrofluorenone.

9. A layer according to claim 1 in which the electronacceptor isheXabromona-phthalic anhydride.

10. A layer, according to claim 1 in which the electronacceptor istetrachlorophthalic anhydride.

11. A layer according to claim 1 in which the electronacceptor is1,2-benzanthraquinone.

12. A layer according to claim 1 in which the electronacceptor ischloranil.

13. A layer according to claim 1 in which the electronacceptor isdibromomaleic anhydride.

14. A layer according to claim '1 including a resin.-

15. A layer according to claim 1 including adyestutf sensitizer.

16. A photographic reproduction process which comprises exposing .anelectrostatically charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, non-resinous, substantially colorless electronacceptor and acompound having the formula in which R and R are fused ring'ortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl.

17. A photographic reproduction process which comprises exposing anelectrostatically charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, non-resinous, substantially colorless electronacceptor and acompound having the formula in which R and R are fused ringortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl; the layer containing the photoconductor andthe electron-acceptor in proportions ranging from substantially lessthan equal amounts to a substantial excess of the photoconductor withrespect to the electron-acceptor and from substantially less than equalamounts to a substantial excess of the elect-romacceptor with respect tothe photoconductor.

18. A photographic reproduction process which comprises exposing anelectrostatical'ly charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, non-resinous, substantially colorless electronacceptor and acompound having the formula in which 'R and R are fused ringortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl; in proportions ranging from about 0.1 to about300 moles of the electronacceptor per 1000 moles of photoconductor.

19. A photographic reproduction process which comprises exposing anelectrostatically charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, nonresinous, substantially colorless electronacceptor and acompound having the formula in which R and R are fused ringortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl; in proportions ranging from about 0.1 to about300 moles of the photocond-uctor per 1000 moles of theelectron-acceptor.

20. A photographic reproduction process which comprises exposing anelectrostatical'ly charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, nonresinous, substantially colorless electronacceptor and acompound having the formula in which R and R are fused ringortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl; in proportions ranging from about 1 to about50 moles of the electronacceptor per 1000 moles of the photoconductor.

21. A photo-graphic reproduction process which comprises exposing anelectrostatically charged, supported, photoconductive insulating layerto light under a master and developing the resulting image with anelectroscopic material, the photoconductive layer comprising at leastone solid, non-resinous, substantially colorless electronacceptor and acompound having the formula in which R and R are fused ringortho-arylene groups, at least one of the rings having a primary aminegroup attached thereto, and R is selected from the group consisting ofhydrogen and lower alkyl; in proportions ranging from about 1 to about50 moles of the photoconductor per 1000 moles of the electron-acceptor.

22. A process according to claim 16 in which the electron-acceptor is2,4,7 -trinitrofluorenone.

23. A process according to claim 16 in which the electron-acceptor istetranitrofluorenone.

24. A process according to claim 16 in which the electron-acceptor ishexa'b-romonaphthalic anhydride.

25. A process according to claim 16 in which the electron-acceptor istetrachlorophthalic anhydride.

26. A process according to claim 16 in which the electron-acceptor is1,2-benzanthraquinone.

27. A process according to claim 16 in which the electron-acceptor ischloranil.

28. A process according to claim 16 in which the electron-acceptor isdibromomaleic anyhdride.

29. A process according to claim 16 in which the layer includes a resin.

30. A process according to claim 16 in which the layer includes adyestuff sensitizer.

References Cited by the Examiner UNITED STATES PATENTS 3,037,861 6/1962Hoegl et al. 961 3,113,022 12/1963 Cassiers et a1. 961 3,155,503 11/1964Cassiers et a1. 961 3,206,306 9/1965 Neuge'bauer et al. 961

OTHER REFERENCES Andrews, Chemical Reviews, 54: 713-777, October 1954.

Czekal'la et al.: Chemical Abstracts 52: 4317b (1957).

Schneider and Compton et al.: Journal of Chemical Physics, vol. 25: 358,1075-1076 1956.

NORMAN G. TORCHIN, Primary Examiner.

C. E. VAN HORN, Assistant Examiner.

1. A SENSITIZED PHOTOCONDUCTIVE LAYER COMPRISING AT LEAST ONE SOLID,NON-RESINOUS, SUBSTANTIALLY COLORLESS ELECTRON-ACCEPTOR, AND A COMPOUNDHAVING THE FORMULA